1. Field of the Invention
The disclosed embodiments relate to Zener diodes and, more particularly, to an isolated Zener diode structure having a scalable reverse-bias breakdown voltage (Vb), to an integrated circuit incorporating multiple instances of the Zener diode, at least two of which have different reverse-bias breakdown voltages, to a method of forming the Zener diode and to a design structure for the Zener diode.
2. Description of the Related Art
Zener diodes, like conventional diodes, allow current to flow in a forward direction. However, Zener diodes exhibit a reverse-bias breakdown voltage (Vb) that is low relative that of conventional diodes. Specifically, in the case of a conventional diode, current typically does not flow, when the diode is reverse-biased (i.e., when the voltage on the N-type cathode region of the diode is greater than the voltage on the P-type anode region). However, a large breakdown current will flow, when the diode is reverse-biased and the voltage on the N-type cathode region exceeds the reverse-bias breakdown voltage (Vb). In the case of a Zener diode, the reverse-bias breakdown voltage (Vb) is relatively low. As a result, Zener diodes can be used to protect other circuits against over-voltage conditions. For example, Zener diodes can be used as voltage regulators or as electrostatic discharge (ESD) protection circuits.
Unfortunately, in order to achieve such a relatively low reverse-bias breakdown voltage (Vb), additional masking and doping processes are required to either form the P-type anode region or N-type cathode region of the Zener diode or to add an additional amount of dopant to an already formed P-type anode region or N-type cathode region of the Zener diode. These additional masking and doping processes can be costly and time consuming. Thus, there is a need in the art for a Zener diode structure and method of forming the structure that allows a desired, relatively low, reverse-bias breakdown voltage (Vb) to be achieved without requiring additional masking and doping processes.